Sudden drop in performance

I have a pretty powerful PC (ryzen 3900x + 3090, 16gb ram) with a ultra wide monitor (32:9) and the game runs just fine sometimes a couple of hours, then all of a sudden the screen starts to flash black, then to desktop, and the game runs at 7-9 fps almost freezing my whole PC. Once I then restart the game, its stuck at 7-9 fps for some reason till I restart my PC, how is this even possible? I have no idea whats going on.